The present invention relates generally to multilumen catheter assemblies, and more particularly to multilumen catheter assemblies having a smooth, rounded unitary catheter portion for positioning at a vessel wall insertion site and independent, free floating catheter tubes for positioning within an area to be catheterized.
Catheters for the introduction or removal of fluids may be located in various venous locations and cavities throughout the body for the introduction or removal of fluids. Such catheterization may be performed by using a single catheter having multiple lumens. A typical example of a multiple lumen catheter is a dual lumen catheter in which one lumen introduces fluids and one lumen removes fluids. Catheterization may also be performed by using separate, single lumen catheters inserted through two different incisions into an area to be catheterized. Such multiple catheter assemblies are known as Tesio catheters. Procedures are also known as described in U.S. Pat. No. 5,624,413 for inserting two wholly independent single lumen catheters into a vessel through a single insertion site.
Generally, to insert any catheter in a blood vessel, the vessel is identified by aspiration with a long hollow needle in accordance with the Seldinger technique. When blood enters a syringe attached to the needle, indicating that the vessel has been found, a thin guide wire is then introduced, typically through a syringe needle or other introducer device, into the interior of the vessel. The introducer device is then removed leaving the guide wire within the vessel. The guide wire projects beyond the surface of the skin.
At this point, several options are available to a physician for catheter placement. The simplest is to pass a catheter into the vessel directly over the guide wire. The guide wire is then removed leaving the catheter in position within the vessel. However, this technique is only possible in cases where the catheter is of a relatively small diameter, made of a stiff material and not significantly larger than the guide wire, for example, for insertion of small diameter dual lumen catheters. If the catheter to be inserted is significantly larger than the guide wire, a dilator device is first passed over the guide wire to enlarge the hole. The catheter is then passed over the guide wire, and the guide wire and dilator are removed.
In the case of an individual, single-lumen catheter typically used in multiple catheter assemblies (e.g., a Tesio catheter), a physician may use an introducer sheath. If a Tesio catheter is used for hemodialysis, for example, each catheter is inserted in two separate veins, such as the femoral vein. Alternatively, each catheter may be inserted in two different locations of the same vein, such as the internal jugular vein as noted above. The introducer sheath is simply a large, stiff thin-walled tube, which serves as a temporary conduit for the permanent catheter which is being placed. Tearaway sheaths are also available which split apart for easier removal. The introducer sheath is positioned by placing a dilator device inside of the introducer and passing both the dilator and the introducer together into the vessel over a guide wire. The guide wire, left in the vessel after insertion as described above, and the dilator are then removed, leaving the thin-walled introducer sheath in place. The catheter is placed through the introducer sheath. Each of the catheters in the assembly is typically subcutaneously secured within the patient""s body by a cuff located in a subcutaneous tunnel, or by otherwise externally affixing the catheter to the body.
The Tesio catheter may also be inserted, in accordance with the technique described in U.S. Pat. No. 5,624,413, as noted above, through a single insertion point using a sheath into the vessel. The Tesio catheter, once inserted in the vessel, is then tunneled separately through the patient in two subcutaneous tunnels for securement of the external, proximal portions of the catheter.
The Tesio double catheter assembly, while comfortable for the patient, due to its soft durometer, and very effective for hemodialysis, typically requires multiple procedures and incisions for insertion and/or for tunneling, which increase the attendant risks of the catheterization procedure. Further, in the case of side-by-side placement of two catheter tubes through a single insertion site in a vessel, while minimizing the number of procedures, can present a potential for leakage between the catheter tubes at the point where the catheter tubes pass into the vessel.
However, Tesio catheter assemblies provide catheters which are capable of independent movement within the vessel. Such catheters present several advantages over unitary multilumen catheters formed of a single internally divided tube when in the vessel. Because the individual tubes of a Tesio double catheter assembly are independently movable at their fluid outlets, it is possible to provide fluid intake and/or return flow around the entire circumference of the distal ends of the catheter tubes. In addition, if one tube becomes blocked, or otherwise requires replacement, it can be removed independently of the other tube. Further, the softer durometer of such catheters, which are typically made of a silicone or a similar material, reduces the risk of vessel wall damage. The 360xc2x0 circumferential flow provides a more stable tube within the vessel, which is less likely to be suctioned against the vessel wall due to a pressure differential, as occasionally occurs in the use of some side-by-side multi-lumen catheters.
U.S. Pat. No. 5,718,692, issued to Schon, et al., (xe2x80x9cthe Schon catheterxe2x80x9d) describes a self-retaining double catheter system in which each catheter can be subcutaneously secured without the use of fabric tissue ingrowth cuffs or external suturing as a result of the placement of a retaining sleeve surrounding both individual catheters in a multiple catheter assembly to hold the catheters together at the location of the sleeve. The individual catheters are permanently linked in one portion by a hub for self-anchoring under the skin, as an alternative to requiring a fabric stabilizing cuff, such that such cuffs are optional. The distal ends are longitudinally prespaced by an appropriate distance to avoid recirculation. While this device requires only one incision, it requires two subcutaneous tunnels in order to facilitate the self-retaining feature. This catheter provides independently movable distal ends within the vessel and 360xc2x0 circumferential flow in the manner of a standard Tesio. Further, since the retaining sleeve is located outside the vessel when in place to provide the self-retaining feature, at the point of entry into the vessel, the catheters are side-by-side in the manner of a standard Tesio catheter, and there still remains the potential risk of blood leakage between the catheters at the vessel site.
U.S. Pat. No. 5,947,953 discloses a splittable multiple catheter assembly that has a hub and at least two fully independent catheter tubes which are initially releasably joined together, for example, by a breakable membrane. A single subcutaneous tunnel may be used in inserting the catheter, and the catheter tubes are at least partially separated by splitting the catheter tubes prior to insertion into a vessel. As a result, the portions of the catheter within the vessel are capable of independently moving and having 360xc2x0 circumferential flow from the distal portion of each tube. The catheter may be secured using standard securement means such as suturing, ingrowth or other available securement devices.
A further multiple catheter assembly is described in U.S. Pat. No. 5,776,111 for use in acute Tesio catheterizations. The assembly includes two independent single lumen catheters joined at a location by a generally flat disc that may be attached to the surface of a patient""s skin to secure the assembly in an acute procedure. The distal ends are prespaced to avoid recirculation.
There is a need in the art for a multiple catheter assembly and a need for making such a catheter assembly which can provide the advantages of the above-mentioned multi-lumen catheters with respect to easy insertion through a single tunneling procedure and which can prevent the potential risk of leakage at the site of vessel entry, but which can still provide the advantage of multiple catheter assemblies with respect to independent movement within a vessel and good flow properties.
The present invention is a multilumen catheter assembly which provides easy catheter insertion by a single tunneling procedure and assists the prevention of leakage at the site of vessel entry through use of a unitary, outer wall configuration. The catheter assembly also provides independent, free floating movement within the vessel through use of separate, distal end catheter tubes and provides efficient fluid flow properties within lumens of the catheter assembly.
In one aspect of the present invention, the multilumen catheter assembly includes a unitary portion having an outer wall, a distal end, a proximal end, and a plurality of lumens extending longitudinally through the unitary portion. In this aspect, the catheter assembly also includes a plurality of distal end tubes, each defining a longitudinally extending lumen therethrough, where the lumens of the distal end tubes are each in fluid communication with a respective lumen of the unitary portion, and the distal end tubes are capable of independent movement with respect to each other. In this aspect of the invention, the outer wall of the unitary portion, the outer wall of the distal end tubes, and the lumens, can have various shapes in cross section, such as but not limited to a circular, semi-circular, or oval shape. The unitary portion, the distal end tubes, and the lumens, can also have a different shape or configuration at different points along a respective longitudinal length of each.
In another aspect of the present invention, the multilumen catheter assembly includes a unitary catheter having an rounded exterior surface, a first lumen and a second lumen extending longitudinally therethrough, a distal end and a proximal end; and a first distal end tube defining a first longitudinally extending passageway and a second distal end tube defining a second longitudinally extending passageway, where the first and the second distal end tubes extend distally from the distal end of the unitary catheter, the first passageway in the first distal end tube being in fluid communication with the first lumen, the second passageway in the second distal end tube being in fluid communication with the second lumen and the first and second distal end tubes are capable of independent movement with respect to each other.
In another aspect of the present invention, the distal end tubes are releasably attached to one another over a portion, or the entirety, of their longitudinal length, allowing the first and the second distal end tubes to be split, through use of minimal force, and separate over any portion of their longitudinal length.
In another aspect of the present invention, the first and the second distal end tubes are releasably attached to one another, and possibly having an outer wall with semi-circular cross section, from the distal end of the unitary catheter to a bonding point located between the distal end of the unitary catheter and the distal end of the catheter assembly, allowing the first and the second distal end tubes to be split, through use of minimal force, to any longitudinal point between the distal end of the unitary catheter and the transition point, the first and the second distal end tubes being separate from one another, and possibly circular in cross section, from the transition point to the distal end of the catheter assembly, providing the first and the second distal end tubes with individual and independent movement with respect to each other from the transition point to the distal end of the catheter assembly. In this aspect of the present invention, the unitary catheter can have a generally oval cross section.
In another aspect of the invention, the multilumen catheter assembly includes two catheter tubes, each having a round lumen extending longitudinally therethrough and each having an exterior of generally semi-circular cross sectional shape. In this aspect, the catheter assembly also includes a hub securing the two catheter tubes in juxtaposed alignment with respect to one another, wherein the tubes in juxtaposed alignment together have a generally oval shape in cross section.
The present invention also provides a method for making a multilumen catheter assembly, the method includes forming a unitary catheter tube having a proximal portion and a distal portion, the distal portion terminating at a distal end and the proximal portion terminating at a proximal end, the unitary catheter tube having a first lumen and a second lumen, the first lumen and the second lumen each extending longitudinally through the unitary catheter tube. The formed unitary catheter tube is then split longitudinally along the distal portion to form a first distal end tube and a second distal end tube. The unitary catheter tube, the distal end tubes, and lumens within each, can each then be finished, if desired, to have one or more configurations, or cross sectional shapes, over a respective longitudinal length of each.
In one aspect of the present invention, the distal end tubes are then releasably attached along any portion, or an entirety, of their longitudinal lengths. In another aspect, the distal end tubes are releasably attached from a transition point (the point of transition, after splitting, between the unitary catheter and the first and the second distal end tubes) to a bonding point located between the transition point and the distal end of the catheter assembly.